This invention relates to organopolysiloxane gum emulsions. More particularly, this invention relates to an organopolysiloxane gum emulsion that can be used as a cosmetic base, lustrant, lubricant, antifoam, fiber-treatment agent, and paint additive.
Emulsions of high-viscosity organopolysiloxanes are used as cosmetic bases, lustrants, antifoams, lubricants, and fiber-treatment agents. These emulsions of high-viscosity organopolysiloxanes have generally been prepared by the strong acid-catalyzed or strong base-catalyzed emulsion polymerization of an organosiloxane oligomer having a low degree of polymerization (DP) i.e. Japanese Patent Publication Numbers Sho 34-2041 [2,041/1959] and Sho 41-13995 [13,995/1966].
However, due to the use of a strong acid or strong base as the polymerization catalyst, the emulsions afforded by these emulsion polymerization methods take the form of very highly ionic anionic or cationic emulsions. One problem with these emulsions is that their stability is strongly impaired when they are employed in combination with counterionic additives. Moreover, these methods provide poor control over the DP of the organopolysiloxane making up the emulsion, and they also suffer from limitations in terms of DP. These problems have resulted in attempts at emulsion preparation by emulsification by mechanical means of organopolysiloxanes already having a high viscosity. Unfortunately, it has generally proven to be quite difficult to prepare stable emulsions by the emulsification in water of high-viscosity organopolysiloxanes. Attempts have been made to first reduce the viscosity by dissolving the high-viscosity organopolysiloxane in a suitable diluting solvent, and then carrying out emulsification using a mechanical agitator such as a colloid mill, or homogenizer. However, the resulting emulsion necessarily contains the diluting solvent, which can impair the properties expected from the high-viscosity organopolysiloxane in the ultimate application. This problem prevents the use of these emulsions in some applications.
Japanese Patent Publication Number Sho 46-10162 [10,162/1971] teaches the homogenization of a dimethylpolysiloxane oil (viscosity at 25.degree. C.=500,000 centistokes), emulsifying agent, and water by mixing on a three-roll mill followed by dilution of the resulting mixture with water. No mention is made, however, of emulsions of organopolysiloxane gums, whose viscosities at 25.degree. C. exceed 1,000,000 centistokes. Japanese Patent Application Laid Open [Kokai or Unexamined] Number Hei 4-230309 [230,309/1992] in Examples 1-3 discloses examples of emulsion preparation by mixing a dimethylpolysiloxane with a viscosity at 25.degree. C. of 1,000,000 centistokes, emulsifying agent, and water in a homomixer. Also disclosed therein are Examples 4-6 of emulsion preparation by mixing in a homomixer, water, emulsifying agent, a low-viscosity dimethylpolysiloxane oil, and a dimethylpolysiloxane gum with a viscosity at 25.degree. C. of 7,000,000 centistokes or 10,000,000 centistokes.
One drawback to the emulsions of the high-viscosity dimethylpolysiloxane as disclosed in Japanese Patent Application Laid Open [Kokai or Unexamined] Number Hei 4-230309 [230,309/1992] is their low dimethylpolysiloxane content of 0.1 to 10 weight%. In regard to the dimethylpolysiloxane emulsions of Examples 1 to 3, these have a poor stability, with the result that the water and high-viscosity dimethylpolysiloxane separate when these emulsions are allowed to stand for long periods of time. Drawbacks can occur with the dimethylpolysiloxane emulsions of Examples 4 to 6 because they contain dimethylpolysiloxane oil. For example, the use of such emulsions as a cosmetic base results in a poor resistance to washing, and in sensations of refreshment and lightness that are weak, and in particular not longlasting. When used as lustrants, such emulsions give an unsatisfactory luster durability, and when used as water repellents, they give a poorly durable water repellency. These drawbacks place limitations on the use of these emulsions.
We discovered that the use of a mixing device equipped with a special agitation mechanism makes possible the easy preparation of emulsions of very high-DP high-viscosity organopolysiloxanes, i.e., organopolysiloxane gums. This method has been disclosed in our Japanese Patent Application Number Hei 7-9248 [9,248/1995]. The present invention was achieved based on the discovery that the emulsions afforded by this method solve the problems described hereinbefore.